This invention relates to an automatic sharpener for chain saws.
Saw chains of a chain saw are sometimes sharpened by an sharpener which pushes a grindstone from a retracted position to a position in a passage through which the teeth of the saw chain are moved, this position being the position at which the teeth of the saw chain are automatically set. A conventional automatic sharpener for chain saws is, for example, constituted in such a manner that a grindstone secured by its shaft is held at a retracted position by means of a compression spring, and when the teeth of the saw chain are set, the grindstone is pushed and held by the operator's finger against the force of the compression spring to the position at which the teeth of the saw chain are set. In order to adjust the setting of the grindstone, the dial of a setting adjustment portion disposed on the shaft of the grindstone is turned so that the shaft of the grindstone is moved slightly forward or rearward. In a conventional automatic sharpener of the type described above, it is necessary for the grindstone to be pushed to and then held against the force of a spring by the operator's finger at the position where the teeth are to be set. Furthermore, the structure of the setting adjustment portion is very complicated, and the size of the automatic sharpener is thus relatively large so that there are sometimes limitations when it is mounted on the main body of the chain saw.